The problem appearing in tunnels, especially the longer ones, is how to ensure the removal of contaminated gas from the tunnel in an easy and efficient way, combined with quick and efficient fire extinguishing without a spread of smoke into the part of the tunnel not affected by fire. The Invention solves these technical problems by providing a stationary air flow in the tunnel applying a ventilation system and a tunnel ventilation process, where the ventilation section above the horizontal partition is divided by vertical partition walls into three separate ventilation ducts. In the ventilation ducts are flaps, which, unlike the standard shutters, provide perfect sealing. Furthermore, the system consists of a ventilation unit installed in an engine room on tunnel portals, which allows servicing of the unit without interference in current traffic. Due to continuous discharge of contaminated air from the tunnel, the ventilation and ventilation control equipment ensures in both normal operation and fire conditions minimum pollution of the tunnel's walls and ceiling. The tunnel ventilation control system also allows the return of air to where it was drawn out, with a result that no major microclimate changes occur. The system allows installing a purification system to get contaminated gases out of the tunnel. The system as a whole is designed for low energy levels, requiring optimum energy consumption for its operation. If fire breaks out in the tunnel, the system and process according to the invention ensure that fire is confined to a stationary space between two adjacent rows of flaps, whereby one of the main features of the Invention is materialized to the effect that the spread of smoke into the rest of the tunnel is contained, because there is no fresh air motion through the fire; through the flaps smoke is directly carried away via lateral and, if needed, middle ducts, and fresh air comes from both portals to the flaps in front of the fire and, if needed, partly also to the middle duct. Simultaneous with fire signalling and detection of the exact position of fire, air with reduced oxygen content is introduced into the fire section, whereby fire extinguishing takes place. Fresh air motion to the flaps in front of the fire and simultaneous discharge of contaminated air and smoke through at least two ventilation ducts limit the spread of smoke in the tunnel and thereby provide free access for rescuers arriving from any side of the tunnel. Salvage operation is made possible by abandoning the fire zone towards any side and finally the free exit from the tunnel. Apart from fire extinguishing by means of reduced oxygen air, the system allows fire extinguishing by using other agents and systems.